Optical switching switching and attenuation systems and methods therefor

ABSTRACT

Novel light switches and attenuators are disclosed. In one form of the invention, a novel 2×2 crossbar switch is formed by positioning a movable reflector intermediate four fiberoptic lines. In another form of the invention, a 1×N switch is formed by providing a plurality of cantilevers each having a reflective surface thereon. In still another form of the invention, a novel light attenuator is formed by positioning a movable arm intermediate two fiberoptic elements.

REFERENCE TO EARLIER APPLICATIONS

[0001] This application claims the benefit of pending prior U.S.Provisional Patent Application Serial No. 60/079,994, filed Mar. 30,1998, by Tayebati et al., entitled OPTICAL SWITCHING USINGMICRO-ELECTROMECHANICAL TECHNIQUE; and pending prior U.S. ProvisionalPatent Application Serial No. 60/105,940, filed Oct. 28, 1998 by Azimiet al., entitled VARIABLE OPTICAL ATTENUATOR. The two aforementioneddocuments are hereby incorporated herein by reference.

FIELD OF THE INVENTION

[0002] This invention relates to optical systems in general, and moreparticularly to switches and attenuators for use in optical systems.

BACKGROUND OF THE INVENTION

[0003] In many situations, it is necessary to switch or attenuate alight signal within an optical system.

[0004] By way of example but not limitation, in a typical opticalsystem, it may be necessary to switch a light signal between a firstline and a second line.

[0005] By way of further example but not limitation, in a typicaloptical system, it may be necessary to attenuate a light signal passingthrough a line.

OBJECTS OF THE INVENTION

[0006] One object of the present invention is to provide novel apparatusfor switching a light signal in an optical system.

[0007] Another object of the present invention is to provide novelapparatus for attenuating a light signal in an optical system.

[0008] Still another object of the present invention is to provide anovel method for switching a light signal in an optical system.

[0009] Yet another object of the present invention is to provide a novelmethod for attenuating a light signal in an optical system.

SUMMARY OF THE INVENTION

[0010] These and other objects of the present invention are addressed bythe provision and use of novel light switches and attenuators. In oneform of the invention, a novel 2×2 crossbar switch is formed bypositioning a movable reflector intermediate four fiberoptic lines. Inanother form of the invention, a 1×N switch is formed by providing aplurality of cantilevers each having a reflective surface thereon. Instill another form of the invention, a novel light attenuator is formedby positioning a movable arm intermediate two fiberoptic elements.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Still other objects and features of the present invention will bemore fully disclosed or rendered obvious by the following detaileddescription of the preferred embodiments of the invention, which is tobe considered together with the accompanying drawings, wherein likenumbers refer to like parts and further wherein:

[0012]FIG. 1 is a schematic side view showing a novel 2×2 crossbarswitch in a first state;

[0013]FIG. 2 is a schematic side view showing the 2×2 crossbar switch ofFIG. 1 in a second state;

[0014]FIG. 3 is a schematic side view showing an alternative form of 2×2crossbar switch;

[0015]FIG. 4 is a schematic view showing a 1×N optical switch formed bya plurality of cantilevers;

[0016]FIG. 5 is a schematic view showing a novel light attenuator formedin accordance with the present invention;

[0017]FIG. 6 is a schematic view showing a portion of the lightattenuator of FIG. 5 in various states of operation;

[0018]FIG. 7 is a schematic view showing the light attenuator of FIGS. 5and 6 positioned between two fiberoptic elements; and

[0019]FIG. 8 is a schematic view showing the light attenuator of FIGS. 5and 6 used in an alternative setting.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] Looking first at FIG. 1, there is shown a novel 2×2 crossbarswitch 5 formed in accordance with the present invention. Crossbarswitch 5 utilizes a first lens 10 and a second lens 15 to connect afiberoptic element 20 with a fiberoptic element 25, and to connect afiberoptic element 30 with a fiberoptic element 35, when the 2×2crossbar switch is in the state shown in FIG. 1.

[0021] In accordance with the present invention, a substrate 40 ispositioned between lenses 10 and 15. Substrate 40 carries a comb drive45 or some other type of actuation and a moving arm 50 thereon. A hole55 is formed in moving arm 50 so that light can pass between fiberopticelement 20 and fiberoptic element 25, and fiberoptic element 30 andfiberoptic element 35, when the 2×2 crossbar switch is in the positionshown in FIG. 1. A reflector 60, spaced from hole 55, is also carried bymoving arm 55.

[0022] In accordance with the present invention, when crossbar switch 5is to be activated, comb drive 45 is activated so as to move moving arm50, whereby to position reflector 60 at the location where hole 55previously sat. Reflector 60 causes fiberoptic element 20 to beconnected to fiberoptic element 30, and fiberoptic element 25 to beconnected to fiberoptic element 35, when the 2×2 crossbar switch is inthe state shown in FIG. 2.

[0023] Stated another way, in the switch state shown in FIG. 1, thelight signal from fiberoptic element 20 goes through hole 55 inactuating (moving) arm 55 of comb drive 45 and couples to fiberopticelement 25. Similarly, fiberoptic element 30 is coupled to fiberopticelement 35. This is the “through connect” situation. When voltage isapplied to comb drive 45, arm 50 moves to a new position and bringsreflector 60 in the path of the light beams, so that the switch is inthe state shown in FIG. 2. In this condition, a light signal fromfiberoptic element 20 is reflected and couples back to fiberopticelement 30 and, in similar fashion, fiberoptic element 35 will becoupled to fiberoptic element 25. FIG. 2 represents the “cross barswitching” state of the switch.

[0024] The via-hole 65 in substrate 40 provides low insertion loss forthe switch. Alternatively, substrate 40 can be anti-reflection coated.

[0025] The Grin-lenses 10 and 15 provide the proper bending of the lightas shown in FIGS. 1 and 2. Alternatively, thermally expanded core (TEC)fiberoptic elements 20A, 25A, 30A and 35A can be used with appropriatemounts 70, 75 as shown in FIG. 3.

[0026] Looking next at FIG. 4, there is shown a novel 1×N switch 100.Switch 100 utilized three cantilevers 105, 110 and 115 formed on asubstrate 120. Cantilevers 105, 110 and 115 have reflective regions105R, 110R and 115R formed thereon, respectively. Cantilevers 105, 110and 115 are positioned relative to one another, and relative to areflective surface (e.g., a mirror) 120, such that when the cantileversare in a first state, an input beam 125 may be reflected off cantileverreflective region 105R and reflective surface 120 so as to land oncantilever reflective region 110R. However, when cantilever 105 is movedto a second position, e.g., by the application of an electric field,input beam 125 may be reflected off cantilever reflective region 105Rand reflective surface 120 so as to land on cantilever reflective region115R.

[0027] In the same way, properly positioned reflective surfaces 130 and135 can direct light from reflective surface 110R and 115R to outputports 140/145 and 150/155, respectively, depending on the position ofcantilevers 110 and 115, respectively.

[0028] Stated another way, input beam 125 reflects off the tip ofcantilever 105. This reflected beam is further reflected by surface 120placed at an appropriate position, i.e., on top of the cantilevers.Hence, by double reflection, the beam 125 can land on reflective surface110R on the tip of cantilever 110. With an applied voltage to cantilever115, the beam can be switched to reflective surface 115R on cantilever115. In similar fashion, the beam 125 reflecting off cantilever 110 canbe routed (via reflective surface 130) to positions 140 or 145 by theapplication of appropriate voltage to cantilever 110; or the beam 125reflecting off cantilever 115 can be routed (via reflective surface 135)to positions 150 and 155 by the application of appropriate voltage tocantilever 115. In this way, the input beam 125 can be selectivelyswitched (i.e., routed) to output ports 140, 145, 150, and 155, asdesired.

[0029] Looking next at FIGS. 5-7, there is shown an optical attenuator200 also formed in accordance with the present invention. Opticalattenuator 200 comprises a so-called “MEM's” (microelectromechanical)structure 205 disposed between two single mode fibers 210 and 215. Moreparticularly, MEM's structure 205 comprises a substrate 220 having anarm 225 extending therefrom, and an actuator 230 for moving arm 225 intoand out of position between fibers 210 and 215, whereby to selectivelyposition the arm's mirror 235 into and out of the light path 240extending between the two fibers (FIG. 6). The substrate 220 on whichthe microelectromechanically-activated arm 225 is fabricated ispositioned perpendicular to the optical axis of the fibers (FIG. 7).

[0030] The actuator 230 may be any available electromechanical, thermalor magnetic based actuator. One example of an electromechanical actuatoris the comb drive 245 shown in FIG. 5. Mirror 235 may be positionedparallel to the substrate 220, or preferably at an angle to thesubstrate, so as to avoid back reflection of the light back into thefiber.

[0031] In order to allow efficient coupling of light between fibers 210and 215, the substrate 220 has a via hole 250 (FIG. 7) on the back toallow the two fibers to be brought close to the arm 225 and to eachother.

[0032] The MEM's structure 205 is designed such the light passingthrough the substrate 220 undergoes no residual reflections from thenon-moving part. For example, the device is fabricated such that afterprocessing, no part of the substrate 220 remains between the two fibers(FIG. 7) or the front and the back of the remaining part of thesubstrate are antireflection (AR) coated as shown at 255 using Si/SiO₂or other multilayer films (FIG. 8).

What is claimed is:
 1. A switch for directing the path of a lightsignal, said switch comprising: a member comprising a hole and areflector; first, second, third and fourth light transmitting elements,said first and third light transmitting elements being disposed on oneside of said member, and said second and fourth light transmittingelements being disposed on the other side of said member; and anactuator for moving said member so as to selectively: (1) position saidhole intermediate said first and second light transmitting elements, andintermediate said third and fourth light transmitting elements, so as tooptically couple said first and second light transmitting elements, andso as to optically couple said third and fourth light transmittingelements; and (2) position said reflector intermediate said first andsecond light transmitting elements, and intermediate said third andfourth light transmitting elements, so as to optically couple said firstand third light transmitting elements, and so as to optically couplesaid second and fourth light transmitting elements.
 2. A switchaccording to claim 1 wherein said first, second, third and fourth lighttransmitting elements comprise fiberoptic elements.
 3. A switchaccording to claim 1 wherein said actuator comprises amicroelectromechanical (MEM) device.
 4. A switch according to claim 3wherein said actuator comprises a MEM comb drive.
 5. A switch accordingto claim 1 wherein a Grin lens is disposed between said first and thirdlight transmitting elements and said member.
 6. A switch according toclaim 1 wherein a Grin lens is disposed between said second and fourthlight transmitting elements and said member.
 7. A switch according toclaim 1 wherein said first, second, third and fourth light transmittingelements comprise thermally expanded core (TEC) fiberoptic elements. 8.A switch for directing the path of a light signal, said switchcomprising: first, second and third cantilevers, each of saidcantilevers having a reflective region formed thereon; means fordeflecting said first cantilever from a first position to a secondposition; and a reflective surface, said reflective surface beingpositioned so as to: (1) receive light reflected off said reflectiveregion of said first cantilever and direct the light to said reflectiveregion of said second cantilever when said first cantilever is in saidfirst position; and (2) receive light reflected off said reflectiveregion of said first cantilever and direct the light to said reflectiveregion of said third cantilever when said first cantilever is in saidsecond position.
 9. A switch according to claim 8, further comprising:means for deflecting said second cantilever from a first position to asecond position; and a second reflective surface, said second reflectivesurface being positioned so as to: (1) receive light reflected off saidreflective region of said second cantilever and direct the light to afirst output port when said second cantilever is in said first position;and (2) receive light reflected off said reflective region of saidsecond cantilever and direct the light to a second output port when saidsecond cantilever is in said second position.
 10. A switch according toclaim 9, further comprising: means for deflecting said third cantileverfrom a first position to a second position; and a third reflectivesurface, said third reflective surface being positioned so as to: (1)receive light reflected off said reflective region of said thirdcantilever and direct the light to a third output port when said thirdcantilever is in said first position; and (2) receive light reflectedoff said reflective region of said third cantilever and direct the lightto a fourth output port when said third cantilever is in said secondposition.
 11. An optical attenuator comprising: a support; an armattached to said support; a mirror attached to said arm; andmicroelectromechanical means for moving said arm so as to selectivelyposition said mirror across a light path extending between two lighttransmitting elements.
 12. An optical attenuator in accordance withclaim 11 wherein said mirror is disposed at a non-perpendicular anglerelative to said light path.